Metal culvert



May 2 8, 1940- D. L. MILLER ET AL METAL CULVERT Filed June 9, 1939 Patented May 28, 1940 UNITED STATES METAL David L. Miller and Alb PATENT OFFICE GULVER'I ert G. Felker, Marshfield,

Wis.

Application June 9, 1939, Serial No. 278,374

' '4 Claims, (01. 138-70) grade line as associated with said culvert, where- Our invention relates to a culvert construction and more particularly to the construction and arrangement of culverts as used for drainage purposes and the like.

We are aware of the fact that culvert structures have heretofore been made of an arched upper portion in the form of a half circle, the

lowermost ends of said arched section being connected by the metal section which defines the bottom or drainage portion of the culvert, which bottom portion has been substantially flat or slightly curved to provide a rounder bottom. We are also aware that culverts so constructed have been made of metal sections corrugated prior to being formed into the structure above defined. We are aware of the fact that culverts so constructed have developed disadvantages, which disadvantages will become apparent when considered in conjunction with our improved culvert.

One of the objects of this invention is to provide better drainage facilities than with the flat or slightly curved bottom type culverts.

Another object is to provide greater drainage area without sacrificing the basic shape present in arch type culverts and without providing any material increase in the amount of metal utilized.

Still another object is to provide for obtaining a self-centering action together with a minimum possibility of lateral shifting of the culvert of the present invention, either at the time of installation or subsequently under shifting of the fill (dirt, stone, gravel, etc., surrounding the culvert) by the action of frost, etc., a feature which is not present in the flat or slightly rounded bottom type culvert.

Another object of our invention is to minimize upward buckling of the bottom portion of the culvert under the upward pressure exerted by frost, etc. v

Another object is to provide an improved culvert construction wherein, by virtue of the minimizing of the buckling action, maximum drainage is provided, and in the absence of "any central buckling (which is present on flat and slight ly rounded type bottom culverts) localized paths of drainage along the sides of the culvert adjacent the lowermost portion of the arch are obviated.

Still another object is to provide-for retaining in the bottom portion of the culvert, gravel, dirt,

etc., to aid in minimizing the corrosive action by the necessity of relaying is eliminated.

Another object of our invention is to provide a culvert structure having less liability of collapsing, due to the truss formation present in the bottom of said culvert, which truss-like structure materially strengthens the arched portion thereof.

- These and other objects will be well understood by those skilled in the art when considered in conjunction with the description which follows and when considered in, conjunction with the drawing showing one embodiment of our culvert structure.

In the drawing:

Figure 1 is a perspective view of a metallic culvert embodying features of the present invention.

Figure 2 is an end view of the culvert of the present invention as shown in Figure 1.

The culvert, of the present invention, is made from metallic sheet, and while not limited thereto, we have shown this metallic sheet as being corrugated and the culvert fabricated from one piece of sheet metal. It is to be understood that such culverts can be of a size which would prohibit the use of a single sheet of either flat or corrugated metal and it is to be understood that we might readily make this culvert from not only a single but also from several sheets welded, bolted, riveted, or otherwise connected, so long as the final structure does not deviate from the construction as shown and hereinafter claimed.

To more clearly define our culvert'construction, we have drawn the line XX between the two lowermost portions of the arched top of the culvert, the arched portion carrying a radius of curvature in equal and opposite directions from the point B. As a general. statement and for purpose of example only, thesides O which define the arch proper, form a half-circle. It is to be understood that the arch may be of a shape other than semi-circular, but we have found the construction as shown to be the most practical when used in conjunction with the particular bottom construction now to be described.

That .portion of the culvert which lies below the line X-X and which is connected to the arched portion at the points X, X, will hereafter be referred to as the bottom portion of the culvert. This bottom portion tapers gradually and downwardly from point X to the point E, thereby forming what is hereafter to be defined as a V, or V-shaped bottom, having opposite half sections which are straight or flat transversely and which incline downwardly and inwardly and meet along a straight line extending in the direction of the longitudinal dimension of the culvert.

We have found that the best results are obtained when the bottom of the V, designated as E lies about one inch below the line X-X, when said line X-X is 12 inches. In other words, the depth of the V-shaped trough should be about 1 inch for every 12 inch width of span. Thus, if the spread of the culvert, as designated by the line X-X, is 24 inches, the distance between point F on the line X-X and point E should be 2 inches. If the line X-X is 36 inches, the distance between the points E and F should be 3 inches, etc. This relation of parts may be otherwise expressed by saying that the opposite straight and flat half sections of the V-shaped f bottom meet at an angle with respect tothe straight line X--X of substantially between 15 degrees and 20 degrees.

We are able to provide approximately 50% more drainage area within that portion XEX than is possible with the fiat bottom type culvert, which increase in drainage area has been made without sacrificing basic shape of the arch type of culvert and without any material increase in the amount of metal utilized.

As is well understood by those skilled in the art of utilizing culverts and providing fill around and about the same, the V-shaped bottom portion of our culvert provides a truss action, which resists the major portion of the upward pressure exerted by frost acting against the bottom of said culvert. This truss also provides additional strength to the sides CC of the culvert, and minimizes any tendency of the arched portion to collapse, thus enabling the placing of more dirt or fill on top of the arched portion. This resistance to the action of frost and greater loadbearing strength gives additional resistance to ,dead weight and load impact as caused by vehicles passing over the roadway when such culverts are placed in roadway drainage positions.

Culverts are placed for drainage in such positions as to have the bottom portion of the culvert aligned with the mean line or grade line of drainage associated therewith. It has been found that when arched type culverts are used where their bottom portions are substantially fiat that the upward pressure of frost, etc. gradually shifts these type of culverts out of alignment with the grade line, which in turn, necessitates removing the fill and relaying the culverts into better alignment with the grade line. This relaying of culverts is avoided in the use of our particular culverts, inasmuch as the buckling action on the bottom portions of our V-shaped culverts is substantially avoided and no misalignment of the bottom of the culvert with the grade line is present to any appreciable extent.

The V-shaped bottom of our culvert provides a wedge type formation into the fill on which the culvert rests. This wedge formation provides a self-centering action to the culvert and practically eliminates any possibility of the culvert shifting laterally at the time the fill is placed over the top of the culvert. It will be readily understood that'should there exist a side pressure on the arched portion C-C of the culvert, such as would have a tendency to laterally shift the culvert as a whole, this type of shifting action would be avoided to a great extent due to the V formation of the bottom of the culvert.

It is desired that culverts, irrespective of their 2,202,743 pe, carry in the bottom or drainage portions thereof, a certain amount of residue such as sand, fine gravel, etc., which will aid in protecting the bottom or drainage portion of the culvert against abnormal erosion. To do this in a conventional rounded bottom culvert would mean that a large portion of the drainage area would be filled with this residue and such construction involves the use of an unnecessary amount of metal which serves no other purpose than to hold this residue.

Arched type culverts having'fiat bottom portions do not of necessity retain this residue, as the very nature of the drainage area prohibits good retention of the residue. We have found in our V-shaped bottom type arched culverts that we do not sacrifice the drainage area yet we are able to provide the surface to retain the residue 'desiredin not too excessive amounts.

It will be understood that as the truss-like action of our V-shaped bottom resists buckling, there is little or no tendency of the central portion to buckle upwardly, with the result that there is more or less uniform drainage and erosive action to the bottom or drainage area of theculvert. If the bottom area is substantially fiat and the central portion buckles upwardly, then the major portion of the drainage lies between the central elevated buckled portion and the lower-1 most sides of the arched walls, thus causing the major drainage and erosion along that portion of the culvert where the sides C connect with the bottom D (areas bounded by the lines (5rI-Iv KL). The average culvert is not continually filled with debris, dirt, water, etc., but only during the peak rainy seasons can this be expected. If the drainage area is along the areas bounded by the points G, H, K and L, that maximum erosion, as well as corrosion, takes place in these areas thus leading to rapid deterioration of the culvert and usually early replacement even before the bottom or true drainage portion of the culvert has even become eroded.

Our particular culvert construction provides for increasing the overall span (line X-X) to provide a great increase in both the drainage and capacity areas without sacrificing the shape desiredand with no material increase in the amount of metal utilized. Thus, for example, if the line X-X is 24 inches and the distance between the points E and F is 2 inches, the capacity area of such a culvert has been increased 4% over that area present if the bottom of the culvert was sub stantially flat. Where culverts of the arched type are desired it will be readily understood by those skilled in the art that the V-shaped trusslike bottom portion of our culvert adds to such arches a strength of structure permitting unusually wide spans of arch because of the strengthening effect of the bottom portion thereof, thus a span or arch can be on the order of six or seven feet providing that the extent of the V portion previously defined is on the order of 1 inchfor every foot of span width.

We claim:

1. A metal culvert of tubular form comprising a V-shaped truss bottom including opposite downwardly and inwardly inclined'fiat portions meeting along a straight line lying'in the plane of the vertical center of the culvert and below the level of I the opposite top edges of the bottom in the ratio of a one inch drop to a one foot of span between said top edges, and an arched top spanning the truss bottom and having its opposite ends supported on the respective opposite ends of the said truss bottom and thereby supported against collapsing strains.

2. A metal culvert having an arched top of substantially semi-circular shape and size, and a truss bottom supporting and sustaining the arched top against collapsing strains and having fiat longitudinal half sections converged inwardly and. downwardly from the bottom edges of the arched top of the culvert, the outer end of each bottom half section being connected with the adjacent lower edge of the top arch by an outwardly convexed curved portion.

3 A hollow metal culvert comprising as its upper portion an arcuate metallic Wall substantially semi-circular in cross-sectional shape and a substantially V-shaped truss bottom portion including oppositely disposed flat metalic walls which are inclined downwardly and inwardly as to converge at a point below a straight line connecting 3 the opposite edges of said upper portion and at a distance therefrom of substantially one inch for each foot of length of said line, said truss bottom supporting the arcuate upper portion against collapsing strains.

4. A hollow metal culvert comprising as its upper portion an arcuate metallic wall substantially semi-circular in cross-sectional shape and a substantially V-shaped truss bottom portion including oppositely disposed flat metallic walls which are inclined downwardly and inwardly as to converge at a point below a straight line connecting the opposite edges of said upper portion, the angle of said flat walls with. respect to the said straight line being substantially between 15 degrees and 20 degrees, said truss bottom supporting the arcuate upper portion against collapsing strains.

DAVID L. MILLER. ALBERT G. FELKER. 

